Method of fabricating piston rings



Feb. 23, 1943.

E. w. SIEGLING 2,311,783

METHOD OF FABRICATING PISTO N RINGS Original Filed 'uar n'r, 1940 2Sheets-Sheet 1 ,1 E. w. SIE-GLING METHOD FABRICATING PISTQN RINGS.

' 2- Sheets-Sheet 2 Original Filed March 7, 1940 Patented F eb. 23, 1943ltIETHOD F FABBIOATING PISTON RINGS Elmer W. Sicgling, Cleveland, Ohio,assignor, by

mesne assignments, to Power Research Corporation, Boston, Mass., acorporation of Massachusetts Original application March 7, 1940, SerialNo.

322,746. Divided and this application September 9, 1940, Serial No.355,922

7 Claims.

This application is a division of my pending application entitledFlexible piston ring, Serial No. 322,746, filed March 7, 1940. Theinvention disclosed in the present application relates to methods offabricating piston rings. More particularly, the invention relates tomethods of making circumferentlally resilient piston rings having spacedupper and lower cylinder wall engaging edges formed by two series ofannularly aligned ring-segments joined by a corrugated annular strip ofresilient sheet metal.

It has heretofore been proposed to fabricate circumferentiallycompressible piston rings having radially disposed tubular oil passagesin three diflerent manners, viz: from a single corrugated metal strip;from a plurality of individual tubes secured together radially; and fromtwo matching corrugated metal strips superimposed axially and weldedtogether.

The present invention departs radically from the prior art by providingmethods of making circumferentially and axially resilient piston ringscomprising two similar series of outer, winged ring-segments ofresilient sheet metal annularly aligned in spaced planes at the samedistance from a common axis together with an inner corrugated annularstrip of resilient sheet metal extending between said planes'and holdingsaid segments in aligned relationship. The large radial openings throughsuch piston rings permit passage of oil therethrough even more freelythan the tubular radial oil passages of the prior art rings. At the sametime the large openings through the rings according to the presentinvention do not become clogged with carbon deposits as do the tubularpassages of the prior art rings.

Such rings may be fabricated by bending a! strip of resilient sheetmetal into a helix having two flat superimposed turns, cutting spacedcircumferentially aligned slots through said strip intermediate theedges thereof, cutting radial slots through said strip extending fromthe outer periphery thereof into communication with said circumferentialslots, and corrugating the inner uncut portion of said strip to decreasethe length of the bent strip into a single turn.

It is therefore an import-ant object of the present invention to providemethods of fabricating axially and circumferentially resilient pistonrings having spaced upper and lower edges for engaging the wall of acylinder and characterized by large radial openings therethrough alwaysopen for free passage of oil between the two peripheral faces of therings.

Another important object of this invention is to provide methods ofmaking piston rings comprising two similar series of outer, wingedringsegments of resilient sheet metal annularly aligned in spaced planesat the same distance from a common axis together with a corrugatedannular strip of resilient sheet metal extending between said planes andholding said segments in aligned relationship in said planes.

A further important object of this invention is to provide a method offabricating the novel rings of this invention involving bending a stripof resilient sheet metal into a helix having two fiat superimposedturns, cutting spaced circuml5 ferentially aligned slots through saidstrip intermediate the edges thereof, cutting radial slots through saidstrip extending from the-outer periphery thereof into communication withsaid circumferential slots, and corrugating the inner 2o uncut portionof said strip to decrease the length of the bent strip into a singleturn.

Otherand further objects of this invention will become apparent from thedisclosures in the specification and the accompanying drawings.

This invention (in a preferred form) is illustrated in the drawings andhereinafter more fully described. 7

In the drawings: 1

Figure 1 is a top plan view of a split ring made according to thepresent invention.

Figure 2 is a greatly enlarged-outside view of the split portion of thering taken along the line II--II of Figure 1.

Figure 3 is a greatly enlarged fragmentary side view of a modified splitarrangement for a ring otherwise similar to the ring of Figure 1.

1 Figure 4 is a fragmentary enlarged side view of a strip of metalillustrating an intermediate stage of fabrication of the ring of Figure1.

Figure 51is agtop plan view of the structure shown in Figure '4.

Figure 6 is a greatly enlarged fragmentary perspective view of the outerface of the ring of Figure 1.

from the insideof a portion of the ring 01', Figure 1. i l Figure 8 isa. cross-sectional view along the line VIII-VIII of Figure 2.

Figure 91s a fragmentary enlarged top plan view of a strip of metalillustrating an inter mediate stage of abrication oi the ring of Figure1 by a modifi ation of the method illustrated in Figures 4 and 5.

Figure 10 is a fragmentary enlarged side view Figure 7 is a greatlyenlarged perspective view i of a strip of metal illustrating anintermediate state of fabrication of the ring of Figure 1 by yet anothermodification of the method illustrated in Figures 4 and 5.

Figure 11 is a greatly enlarged fragmentary perspective view of a dishedpiston ring made according to the principles of the present invention.

Figure 12 is a greatly enlarged cross-sectional view through the ring ofFigure 11.

Figure 13 is a greatly enlarged fragmentary side view of successivestages in the corrugating step in the fabrication of the ring of Figure1 from a metal strip which has been slotted in a prior rearingoperation.

As shown on the drawings:

In Figures 1, 2, 6, '7 and 8 the reference numeral i indicates generallya piston ring made according to the principles of the present invention.This ring comprises an annular strip of resilient sheet metal slottedand corrugated to form winged upper ring-segments Ii annularly alignedon the outside of the ring and similarly aligned winged low rring-segments l2. The segments I I and I2 are held in closely spacedaligned relationship by an inner annular corrugated portion comprisingcrests l3, bottoms l4 and intermediate vertical portions Iii-- As bestshown in Figures 6 and '1, the ring Ill is pierced by a series of spacedcircumferentially aligned slots IB serving to separate the two wings l8of each of the ring-segments H and I2 from the inner corrugated portionof the ring iii, the other parts of the ring-segments being continuouswith the inner corrugated portion. The ringsegments I I and I! areseparated from each other by radial slots l1 equal in number to thecircumferentiai slots i6, piercing the outer periphery of the ring Illand communicating with the slots l6 to form Ts therewith Moreparticularly, the crests l3 and bottoms M of the inner corrugationsextend intermediate the spaced circumferential slots 16. The verticalportions I! of the corrugations are coextensive with the slots l6. Inother words, the radial corners of the corrugations fall at the ends ofthe slots l6. Consequently the outside of each slot l6 which is piercedby a radial slot I1 is divided between the wings of paired uppersegments II and lower segments l2 interconnected by one vertical segmentl5. Similarly the two opposed sides of each radial slot I! are dividedbetween the wings of pairs of upper and lower ring-segments, so that ineach of the Ts formed in the finished ring ID by the slots l6 and I! onepair of adjacent circumferential slots I6 contributes jointly theadjacent parts of the outsides of the slots to form the crossing membersof the Ts while the two radial slots I1 communicating with the p-iredcircumferential slots I! contribute ring-segments. Each segment at onelevel is connected to two therewith overlapping segments at the otherlevel by two opposed, adjacent vertical wall portions [5 of the innercorrugation which thus serve as cross-over segments.

The ring 10 may therefore be described as having upper and lower facesin spaced superimposed relationship, each of said faces comprising aplurality of T-shaped members. The legs of these members are formed bythe crests I! or bottoms i4 and the heads by the ring segments I l andI2, with the wings l8 projecting laterally. The T-shaped members in oneface are staggered with reference to the members of the other face. Thelegs of the members project radially inward in spaced relationship toeach other while the heads are annularly aligned in two planes to definespaced wearing edges for the ring. Intermediate wall members representedby the vertical segments I5 extend between the legs of the staggeredT-shaped members to hold the members together.

As shown in Figures 1 and 2, the ring In may be split as at l9 by aradial slot traversing both a crest l3 and the upper ring-segment Hattached thereto.

Rings made according to the present invention may be split anywhere intheir circumference as long as the surfaces generated by the split arenot prevented from abutting on each other. Figure 3 illustrates a ringmade according to this invention generally indicated by the referencenumeral 30 and comprising upper ring segments 3|, lower ring-segments32, inner corrugations having crests 33, bottoms 34 and verticalcrossover segments 35, circumferential slots (not shown) and radialslots 31 all similar to the jointly their two opposed sides to form theshanks of the T's. This is possible because the upper segments lloverlapthe lower segments I2, as shown in Figure 2, the overlapping portions ofpairs of upper segments ii and lower segments i2 interconnected by onevertical wall portion I! being separated from the corrugated innerportion by one circumferential slot IS. The members of each such pair ofsegments are separated from each other by one radial slot ll.

The above disclosed slotting and corrugation of the annular strip ofresilient sheet metal of the ring i0 yields spaced upper and lower edgesfor engaging the walls of a cylinder composed of two series of annularlyaligned closely spaced winged corresponding features of the ring shownin Figures 1 and 2. However, the ring 30 is split at 38 by a radial slottraversing a cross-over segment 35 of the inner corrugation.

Many other modifications of the ring ID are possible.

Figures 11 and 12 illustrate a ring made according to this inventiongenerally indicated by the reference numeral 40 and comprising upperring-segments 4|, lower ring-segments 42, corrugations having crests 43,bottoms 44 and crossover segments 45, circumferential slots 48 andradial slots 41, all similar to the corresponding features oi the ringof Figures 1 and 2 except that the ring-segments 4| and 42, the crests43 and the bottoms 44 form the same slight angle with the plane of thering 40 to dish the ring.

The upper and lower ring-segments of rings made according to thisinvention are preferably but not necessarily aligned in parallel planes.

Other possible variations include rings in which the radial slots enterthe circumferential slots at the ends of the latter to form Ustherewith. In such rings each ring-segment has only one wing, but thiswing is twice as long as the rings l8 of the ring [0.

The interspaces between the circumferential slots may also be maderelatively long and the corners of the corrugations may be disposed inthe interspaces between the slots being of the same length as the slots.The circumferential slots need not be located exactly halfway betweenthe inner and outer peripheries of the rings.

The distance between the upper and lower ringsegments is a function ofthe curvature of the inner corrugated portion whose length is equal tothe combined lengths of the upper and lower ring-segments.

The edges of the rings engaging the cylinders Rings made according tothis inventionare clr cumferentially compressible, the cross-oversegments such as those indicated by the reference numeral l5 flexing andthe wings l8 approaching each other to take up the gaps therebetween.When so compressed, the rings exert a circumferential spring actiontending to expand the rings radially. This spring action is distributeduniformly over the peripheries of the rings.

The rings are made with peripheries slightly larger than the peripheriesof the cylinders in which the rings are to be installed. n installationthe rings are compressed to an extent such as to leave between the wingsl8v only the minute gaps necessary to take care of expansion due to heatand other irregularities. Such minute gaps are small enough to preventthe leaking therethrough of any appreciable amounts of oil. The outersealing surfaces of the rings are therefore practically continuous.

The compressed installed rings tend to expand against the cylinder wallsso as to bear uniformly against the latter and to adapt themselves tovticularly well adapted to remove excess oil from the cylinder walls. Thelarge openings between K the contact surfaces of the rings and throughthe corrugations permit free drainage of oil therethrough. Theseopenings will further not become clogged by carbon deposits.

Other advantages inherent in rings made ac cording to the presentinvention will be discussed in connection with the hereinbelow followingdisclosure of methods for fabricating the rings.

Figures 4 and illustrate one method of fabrieating the rings of thepresent invention. As shown. a strip of sheet metal having a width equalto the radial width of the ring to be made is bent annular-1y in its ownplane to a radius equal to the radius of the cylinder in which the ringis to be installed. A helix comprising slightly less than two suchcircles required for each ring.

' This initial bending operation gives the required outer curvature tothe ring-segments of the finished rings, thus saving any otherwise nec--essary grinding of the peripheries of the finished rings. Or, to put thematter in different words, the desired shape of the wearing surfaces maybe conferred on the strip of sheet metal in the first fabricatingoperation, this shape remaining intact during subsequent fabricatingoperations, so

that each ring-segment in the finished rings will exactly fit thecylinder bores for which the rings are intended.

In the fabrication of rings having rounded wearing surfaces. the edge ofthe strip that is to form the wearing surfaces is most suitably roundedprior to the bending operation.

The fabrication of the rings is then continued bya slotting and formingoperation. Circumferential slots II and radial slots l'l crossing toform T's are cut in the annularly bent strip which is then bent toapproximately right angles at the ends of the circumferential slots it.Figure '4 shows how the forming operation shortens the helicaily bentstrip into a circle. alternate ring segments being aligned annularly attwo levels with successive segments overlapping.

An alternate method of fabricating the rings of the present invention isillustrated in Figure 9. A strip of metal is first cut and formed andthe slotted and corrugated strip is subsequently bent into annularshape. Such a method yields rings whose outer peripheries would not beperfectly circular so that the rings would have to be ground or machinedround. Further, gaps between the rings would tend to gape outwardly incontrast to the radial slots cut in previously bent strips which formgaps intermediate the rings'which are of uniform width.

' Yet another method of fabricating the ring shownin Figure lis'illustrated in Figure 10. A strip I0 of resilient sheet metal is bentinto a helix having continuous superimposed fiat turns. SubstantiallyT-shaped slots are cut in the helically bent strip. The inner portion ofthe strip is corrugated to decrease its length by approximatelyone-half, and complete turns are 'ing surfaces, and consequently neednot be removed. A cutting operation by methods other than shearing, forinstance, punching or piercing leaves two burrs on the same side of thecut surface. One of these burrs will be on the out-.

side of the corrugated ring and must therefore be removed by grinding orotherwise.

The shearing operation further leaves sharp corners at the intersectionbetween the outer peripheries and the radial slots, no enlarged openingsbeing left at these places which would tend to permit leakage of oiltherethrough. I

It is, of course, possible to fabricate the inner annular corrugatedportions and the outer ringsegments separately and to attach thering-segments to the corrugated portions in a subsequent step by weldingor otherwise.

The rings are preferably made of steel but any other material having thedesired wearing and mechanical properties such as resilience and capableof being machined and formed may be utilized.

After the rings have been formed they at preferably hardened by asuitable heat treatment yielding no rough scale to increase the strengthand resistance to wear. The rings may also be tin plated to give betterwearing surfaces.

Rings made according to this invention are thus easy and inexpensive tomanufacture. The structural features of the rings comprising a radiallycorrugated annular strip of resilient sheet metal and a plurality ofwinged sheet metal ring-segments attached to or integral with theoutside of the corrugated strip at the levels of the crests and bottomsof the corrugations, the ring segments at each level being alignedannularly in closely spaced relationship, coact to confer on the ringsboth uniform axial and circumferential resiliency while at the same timeadapting the rings for removing excess oil from cylinder walls andpermitting oil thus removed to drain through the rings.

As pointed out hereinaltove, various details of construction may bevaried through a wide range without department from the principles ofthis invention and it is, therefore, not the purpose to limit the patentgranted hereon otherwise than necessitated by the scope of the appendedclaims.

I claim as my invention:

1. A method of fabricating a piston ring comprising bending a resilientsheet metal strip having a straight edge into a helix having continuoussuperimposed flat turns, shearing substantially T-shaped slots in theouter portion of the bent strip to form ring segments, said T-shapedslots being of uniform size and uniformly spaced apart along the stripcorrugating the inner portion of the bent strip to decrease its length,the depth of the corrugated portions of the strip corresponding to thelength of the head portions of the T-shaped slots, cutting off completeturns of the thus fabricated stock and maintaining the same curvature inthe helix during the corrugating.

2. A method of fabricating a packing ring comprising bending a resilientsheet metal strip having a straight edge into helical shape, shearingsaid bent strip at uniformly spaced-apart points therealong to formuniform radial slots in the outer portion of said strip and uniformlyspaced apart circumferential slots intermediate the edges of the stripintersecting said radial slots thereby subdividing said outer portioninto spaced winged ring-segments and corrugating the inner portion ofsaid strip along folding lines which intersect the ends of thecircumferential slots to align said ring-segments in closely spacedrelationship in two annular rows which are spaced apart a distancesubstantially corresponding to the length of said circumferential slots.and maintaining the same curvature in the helix during the corrugating.

3. A method of fabricating a packing ring which comprises bending aresilient sheet metal strip having a straight edge into helical shape,

forming radial slots with substantially parallel edges in the outerportion of said strip, cutting circumferential slots intermediate theedges of the strip and intersecting said radial slots, thereby dividingthe outer portion of the strip into spaced segments having radial edges,then corrugat ng the inner portion of said strip by bending the same toform a plurality of leg portions connecting alternate upper and lowercrown portions which include said segments, the distance betweenadjacent lines of bending being so related to the angle of bending thatupper and lower segments are aligned at two levels and maintaining thesame curvature in the helix during the corrugating.

4. A method of fabricating a packing ring which comprises bending aresilient sheet metal strip having a straight edge into helical shape,forming radial slots with substantially parallel edges in the outerportion of said strip, cutting circumferential slots intermediate theedges of the strip and intersecting said radial slots, thereby dividingthe outer portion of the strip into spaced segments having radial edges,then corrugating the inner portion of said strip by bending the samealong a plurality of lines of bending. which lines extend generallyradially of the strip and are spaced apart substantially equal distancesin a direction circumferentially of the strip; said lines of bendingintersecting the circumferential slots and maintaining the samecurvature in the helix during the corrugating.

5. A method of fabricating a packing ring comprising bending a resilientsheet metal strip having a straight edge into helical shape with saidedge outwardly, cutting radial slots into the outer portion of saidstrip, said slots being of uniform length and uniformly spaced apartalong the strip, cutting circumferential slots intermediate the edges ofthe strip to intersect said radial slots thereby subdividing said outerportion K into spaced winged ring-segments, said circumferential slotsalso being of uniform length and having their extremities uniformlyspaced apart from one another, corrugating the inner portion of saidstrip along lines of bending which intersect the ends of thecircumferential slots to align said ring-segments in two annularspaced-apart rows in which the ring-segments of one row are parallel tothe ring-segments of the other row, and maintaining the same curvaturein the helix during the corrugating.

6. A method of fabricating a piston ring comprising bending a resilientsheet metal strip having a straight edge into a helix havingapproximately two superimposed fiat turns, cutting the outer portion ofsaid strip at uniformly spacedapart points therealong to form uniform T-shaped slots therein, with circumferential and radial portions of theslots subdividing said outer portion of the strip into spaced elongatedwinged ring segments, and bending the inner uncut portion of said stripat the end of the circumferential portion of said slots along lines ofbending which converge to move said ring segments alternately intoannular rows which are spaced apart a distance corresponding to thelength of the circumferential portions of the T-shaped slots, whilemaintaining the curvature of the helix and decreasing the length of thestrip into a single turn.

'7. A method of fabricating a packing ring comprising cutting spacedradial slots in the outer portion of a helically wound flat strip ofresilient sheet metal, said strip having its outer edge curved atuniform radius, cutting uniformly spaced apart circumferential slotsintersecting said radial slots to subdivide said outer portion intospaced winged ring segments, corrugating the inner portion of said stripto align said ring segments in closely spaced relationship in annu larrows which are spaced apart a d stance corresponding to the length ofthe said circumferential slots, and maintaining the same curvature inthe helix during the corrugating.

EIMER W. SIEGLING.

